A gas detection system, which comprises a central unit and a plurality of measuring heads on the site, which are connected to the central unit, has been known from DE 38 19 128 C2. Sensors of various types may be interchangeably inserted in the measuring heads, the sensors being provided in the base area with an identification system in the form of soldered contact bridges, with which the measuring head recognizes the sensor that has been inserted. The prior-art identification system requires a plug in the connection area between the measuring head and the sensor with a plurality of plug contacts to transmit the sensor information to the measuring head in a binary coded form. Such multicontact plugs are expensive, on the one hand, and, on the other hand, the fault liability increases with increasing number of plug contacts. In addition, there is only a limited possibility of retrofitting existing measuring heads for new sensor applications, because the plug coding designed originally must be used for compatibility reasons.
So-called transponder chips with integrated data code carriers, which send a signal to a stationary transmitting and receiving means, have been known from another field of application. The transponder chip contains, besides the data code carrier provided with an individual code, a transmitter and a coil acting as an antenna, wherein the transmitter is supplied with voltage or current from the stationary transmitting and receiving means by inductive coupling. The signal that is sent by the transponder chip from the data code carrier enters the transmitting and receiving means over the same path, but in the opposite direction. Such transponder chips are described in EP 716 991 A1.